Method of separating bark from wood.



v F. W. AYER.

METHOD OF SEPARATING BARK FROM WOOD.

APPLICATION FILED MAY 23, 1910.

K222706155 es.-

Patented Dec.27, 1910.

1 TES FRED w. AYER, or BANGOR, MAINE.

METHOD OF SEPARATING BARK FROM WOOD.

Application filed May 23, 1910. Serial No. 562,853.

To all whom it may concern:

Be it known that I, FRED W. AYER, a citizen of the United States, and resident of Bangor, in the county of- Penobscot and State of Maine, have invented new and useful Improvements in Methods of Separating l3 .rk from Wood, of which the following is a specification.

My invention relates to the preparation of wood for paper stock and consists of a process whereby the bark is effectively and economically removed from the wood without wasting any sensible portion of the wood fiber available for paper making.

While my process may be utilized for the separation of bark from wood to prepare the latter for the manufacture of stock for any grade of paper, it is particularly useful in cases where the stock is to be used in the manufacture of the higher grades of paper.

The-preparation of wood pulp for paper making requires the elimination of the bark, for the reason that barkis peculiarly resistant to mechanical or chemical action.

Even small quantities of bark remaining adherent'to wood will pass through all the pulp making processes and retain theform of fiber aggregations and a dark color; to some extent such bark particles find their way even intothe finished paper product, producing blemishes therein known as shives, which lower the value of .the product.- It is important, therefore, to the manufacture of any paper, and-essential to that of high grade paper, that wood bark shall be thoroughly eliminated from the stock. Thus, to be practically and commercially effective, any method of bark removal must be complete and perfect in its results. 40'

This desideratum has been recognized from the earliest days of wood-pulp paper manu facture. facture, bark was removed from the logs at the time of cutting, by means of a chisel-like In the beginning of this manu tool called a spud, and later, by hand shaving at the pulp mill. I Subsequently, barking machines, employing a rotating disk with knives set radially in its face, were introduoed, and are still extensively used for bark removal. These machines are hardly applicable to any material except the round logs,

- and even with such material, their operation is wasteful, because in order to reach the sequent hand shaving to ,remove the bark from these hollows.

Attempts to remove bark from slabs and edgings, which form the largest part of saw mill waste, with these rotary barking machines have not been successful or economical; it is dangerous to handle slabs and edgings in such machines, and the wasteincident to cutting is so large that the expensev of barking saw mill waste has been too large to ustify 1ts conversion into paper stock Thus, slabs and edge strips from'the saw mill have been of little value except as fuel.

and even for this purpose their utility is limited, since their fuelvalue is not high enough to warrant shipment to any considerable distance, and because the large uantity of such waste usually exceeds the fuel demand at the mill where it is produced, and these slabs and edgings, which contain in the aggregate a large amount of wood fiber in itself perfectly adapted to paper manufacture, are for the most part-burned in the open orleft to rot. Moreover, the tops and branches of trees, which are now wasted altogether, contain in the aggregate large quantities of sound wood available for paper making purposes but for the fact that the difiiculty presented by the adhering bark has heretofore prevented their use. It has also been proposed to strip the bark from sticks and logs by means of blades or strippers arranged in a rotary drum in which the logs are tumbled; but this method again has, in practice, -met with only indifferent success for the reason that while there is less waste than by the cutting method, the process isnot sufiiciently thorough. Only those portions of the bark struck by the blades or s'trlppers are removed and bark adhering todepressions or other irregularities in the edges of the wood which become filled with fine fragments of bark and other dirt which must be subseqliently removed with difficulty or if not removed will deteriorate the .quality of the paper stock.

My invention has for itsobject in general the amelioration of the above condition,-the prevention of waste of good wood and the utilization of ,Sticks, slabs, tops, branches I to be subjected to my improve and other small pieces of wood which if successfully deprived ofadhering bark, consti- The slabs tute good available wood fiber. and edge strips produced by the operation 5 of sawing a log into planks, are without further mechanical treatment in pro er shape process. Logs, sticks, tops or branches will. preferably be scored split or sawed longitudinally before being subjected to thisprocess.

The prellminary effect of my process is the liquefaction of the bark cement so that it ceases to have an appreciable adhesive.

value, and the bark is ready to slip or fall off the wood with very little mechanical effort applied to it. Pieces of bark of large The process takes advantage of the fact that the bark of trees ,forms an integument' joined to the wood by cementitious or mucilaginous matter, and that the bark moreover is porous or spongy so that a solvent of the cement may readily penetrate the bark and reduce the cementitious material toa condition resemblingthat of a solution in which its quality as an adhesive is tempo- I rarily, at least, destroyed. Then the cement which secures the bark to the wood is thus softened, loosened, or reduced to solution, it

is quite easy by means ofcomparatively entle mechanical processes, or even'by'han to remove the bark cleanly and completely from the wood. To this end, I immerse the wood, from which the bark is to be removed, in

water, at or approximating the boiling point,

1 kee ingthe wood wholl submerged for a su cient period of time or the hot water to penetrate the bark and dissolve the soluble cementitious or' mucilaginousmaterial which holds the bark to the Wood. By experiments,

chiefly with spruce sticks, consisting of slabs and edgings taken directly from the saw mill I have found that by immersing the wood for about 35 minutes in water at a temperature of from 180 F. to 212 F., the

, cementitious matter holding the bark to the wood will be dissolved, and the bark will become so loosened from the wood as to separate of itself,.-or require only a comparatively gentle mechanical treatment such as attrition caused by making the pieces of wood slide over each other, to remove it.

' The bark in its natural state is of a somewhat porous and spongy structure and tends- C5 to imbibe the water and admit it to the cemflthrough; and upon reaching the cementitious -in an abundance of hot water, which im- 1 throng said in such hot water has two efiects: It

dissolves the intercellular cementitious matter in the bark itself, which binds the bark fibers together and is of the same or similar characterto that which binds the bark to the wood, thus opening the bark to the free and rapid penetration of the hot water therematter' between the bark and the wood it dissolves that and renders the bark easily removable.

At the end of the hot water treatment, if the bark has not separated of itself, it should be stripped or knocked off at once while the wood is wet, otherwise the residual cementitious matter in solution between the bark and the wood, will upon drying, again ,ce- ,ment the bark to the wood. I-therefore subject the sticks to a mechanical stripping treatment after the action of the hot Water and while the cementitious matter is still in solution and hot, to knock or otherwise sepa-' rate the bark from vthe wood, which now only adheresby reason of the suction between the two close fitting wet surfaces.

The above described treatment of split tops, branches, edges and slabs, involves 1mmersion of the bark-carrying Wood pieces pregnates the wood and bark, and supplies enough water, remaining in and upon the pieces, to hold the cementitious matter in solution for a time amply sufficient to allow for mechanical removal of the bark which remains loosely adhering to the wood, after the latter has been taken from the hot water.

In the accompanying drawings is illustrated an apparatus appropriate for, per formin my new process. This apparatus is the oint invention of myself and others" and constitutes the subject of a separate applicationto be filed simultaneously herewith, ointly by myself and others. 120 Figure 1 of said drawings represents a vertical, longitudinal, central sectlon, partly broken away, of an apparatus for removing.

' bark from wood; and Fig. 2 represents a longitudinal section. on broken lines 22 of Fig. 1. a. M

" A represents a long and relatively narrow and shallow tank for holding the water, which is heated by steam introduced jets b, b, leading from the steam upon the chute or incline D. Water is con-' tinuously introduced through pipe P-at the intake end of the tank, so that there is a continuous flow of water through the tank from the intake end to the outlet end, and the belt C is timed to move at substant-iallythe same speed as the stream of water, the belt and stream of water thus carrying thewood forward, and the belt holding it at' all times submerged. The length of the tank and the rate of the supply and overflow of the water I are so proportioned that the submerged wood sticks-occupy about 35 minutes in trav cling from end to end of the tank.

The chute D is'provided with projections preferably arranged staggered or irregularly, as shown, and tumbles the wood about as it falls'down the chute, thus knocking off the bark which has become unglued in the hot water bath. The wood and the separated bark pass down the chute D by gravity, assisted by the overflow stream of water,

- upon a sloping platform E formed of spaced slats. The water and smaller pieces of bark pass through the platform E into a tank T while the wood sticks, entirely cleaned of the bark, and the larger. pieces of bark which cannot pass between the slats of the platform E, slide down platform E into a conveyer F, which carries the material away.

Within the tank T is a screen S'to strain out the bark and the water'is taken from tank T by pipe p and pump 72' to the inletpipe P, thus maintainlng a continuous circulation of the hot water through the apparatus with comparatively little waste of heat.

Said apparatus is herein described merely to illustrate one suitable method of practicing my process, but it will be understood that my process may be performed by other suitable means. i

v The practical result of the above described process, as demonstrated upon a commercial scale, is the saving of from 20% andv upward ofthe sound wood fiber of which the logs and sticks are composed and which has heretofore been wasted, practically increasing the forest yield by that considerable pro: portion.- The percentage saved varies according to the size, and to some extent, the

shape of the logs themselves, and also depends upon the amountof available wood pipe B which is connected withany suitable.

fiber reclaimed by this process from tops.

and branches heretofore wasted.

The effect of the abundance of hot water on the bark-cement isherein expressedby the term solution. I use that, and associated terms of description not in a strict sense; I understand that the effect of water on such mucilaginous matter is not exactly to dissolve it, but to swell and liquefy it, rendering it more and more attenuated, and

' less adhesive, as the proportion of water, or

solvent, increases.

To derive full utility from the above described process, after the bark glue has become thoroughly liquefied by steeping in an abundance of hot water, the scored logs,- sticks, slabs, edgings, etc., should forthwith, that is to say, before the water contained in and carried by them has a chance to become cold or evaporate, be subjected to such gentle mechanical treatment as will peel .or rub off the loosened bark. While this may be done easily by hand, an automatic mechanical treatment is preferable for reasons of economy. All that isnecessary is tocause the wood pieces to slide and rub over each other, the bark covering each piece will then come off, usually as a single strip, leaving the wood clean and bare, stripped of bark even in the depressions. Preferably the bark-stripping is done after the wood pieces are removed from the 'steep'ing-bath;'attrition between the pieces while immersed in water, lwhlle reasonably efi 'ectlve, 1snot so economical, since the flotation and lubricant effect of the water to a degree interferes with the effective rubbing of one piece on another. The reduction of the bark-cement by this method brings to bear two effective agents,.

heat and anabundance of water, as distinguished from the heat alone'whichmight be furnished by steam, or moisture alone as would be supplied by wateratbrd'inary or even warm temperatures. For practical purposes a minimum temperature of 12Q Fahrenheit is requisite, the preferred temperatures lie between 180- Fahrenheit and boiling point.

Iclaim:

1. The method of loosening bark from wood which consists in immersing piecesof wood with bark attached in anabundance of water in-liquid as distinguished from vaporous condition, at a minimum temperature of 120 Fahrenheit for 'such time as suflices to so far liquefy all the cementitious matter binding the bark to the'wood" that it loses its character as an effective ad;

hesive, and so that the wood-and bark are impregnated with sufiicient water to hold said cementitious matter inliquefied condition fora considerable time.

'2. The method of loosening bark wood which consists in immersing pieces of wood with ba'rk' attached in an-abundafice 130 from nientitious matter: between thebark and the of water in liquid as distinguished he wood and impregnating the wood and bark 5 1 'vaporous conditlon, at a minimum tel'npera with sufiicient water to hold said cementiture of 120 Fahrenheit for'sucli time as 'tiousmatter in such liquefied condition as sufiices' to so far liquefy, all the" cementi renders the bark capable of removal from a 5 tious matter binding the bark to the 'wood the wood in its entirety by the aid of gentle that it losesits character as an effective ad mechanical treatment such as the attrition 40 hesive', and so that the wood and bark are of one piece of wood upon another, and impregnated with sufficient water to hold subsequently, while the cementitious matter said cementitious matter in *li uefied conis still liquefied, subjecting the pieces of 10 ditiorf for a considerable time, t en removwood to such mechanical treatment.

ing the pieces of wood from the water and 5. The method of denuding wood of its subjecting them to mutual attrition while 'bark to make it suitable for paper pulp the cementitious matter is still thus liquefied. which consists in steeping the bark covered 7 3.-'The.method of separating bark from wood by immersion in an abundance of' 15 wood which consists in severing the bark water at a temperature between 180 Fah- .1

covering of pieces of wood along the grain, renheit and boilingpoint, thereby liquefyimmersing. the wood thus prepared in an ing all the cementitious matter between the abundance of water in liquid as distinbark and the Wood and impregnating the guished from ,vaporous condition, at a miniwood and bark wit-h'sufiicient water to hold 0 mum temperature of 120 Fahrenheit for said cementitlous matter in such liquefied such time as suflices to so far liquefy all the condition as renders the bark capable of cementitious matter bind-ing the bark to the removal from the Wood in its entirety by wood that it loses its character as an eflecthe aid of entle mechanical treatment such tiveadhesive andsothatthe Wood and bark as the attrition of one piece of wood upon 5 are" impregnated with suflicient water to another, and subsequently, while the cemenhold said cementitious matter in liquefied titious matter-is still llquefied, subjecting condition for a considerable time, the pieces of wood to such mechanical treat- 4., The method of denuding wood of its ment. I i bark to 'malie it suitable for paper pulp Signed by me at Bangor, Maine, this 30' which consists steeping the bark covered twentieth day of May,'1910.

- wood -byimmersion in an. abundance of Q FRED W. AYER. water at a'minimum tern erature of Witnesses: Fahrenheit thereby lique ying all the ce- JOHN C. WILsoN,

FRED R, Awm. 

